linux-kernel - [PATCH v3] tpm: do not suspend/resume if power stays on

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Date:   Fri,  3 Mar 2017 17:09:59 +0100
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     Rob Herring <robh+dt@...nel.org>, Peter Huewe <peterhuewe@....de>
Cc:     Mark Rutland <mark.rutland@....com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        tpmdd-devel@...ts.sourceforge.net,
        Sonny Rao <sonnyrao@...omium.org>
Subject: [PATCH v3] tpm: do not suspend/resume if power stays on

From: Sonny Rao <sonnyrao@...omium.org>

The suspend/resume behavior of the TPM can be controlled by setting
"powered-while-suspended" in the DTS. This is useful for the cases
when hardware does not power-off the TPM.

Signed-off-by: Sonny Rao <sonnyrao@...omium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
---
Changes since v2:
 Jarkko Sakkinen
  - Add a new TPM_CHIP_FLAG_ALWAYS_POWERED flag instead of using a boolean variable.
  - Remove a trailing newline.
Changes since v1:
 Jason Gunthorpe :
  - Move the code to handle suspend/resume in the common chip code.

 Documentation/devicetree/bindings/security/tpm/tpm-i2c.txt | 6 ++++++
 drivers/char/tpm/tpm-interface.c                           | 3 +++
 drivers/char/tpm/tpm.h                                     | 1 +
 drivers/char/tpm/tpm_of.c                                  | 3 +++
 4 files changed, 13 insertions(+)

diff --git a/Documentation/devicetree/bindings/security/tpm/tpm-i2c.txt b/Documentation/devicetree/bindings/security/tpm/tpm-i2c.txt
index 8cb638b..85c8216 100644
--- a/Documentation/devicetree/bindings/security/tpm/tpm-i2c.txt
+++ b/Documentation/devicetree/bindings/security/tpm/tpm-i2c.txt
@@ -8,6 +8,12 @@ Required properties:
                    the firmware event log
 - linux,sml-size : size of the memory allocated for the firmware event log
 
+Optional properties:
+
+- powered-while-suspended: present when the TPM is left powered on between
+                           suspend and resume (makes the suspend/resume
+                           callbacks do nothing).
+
 Example (for OpenPower Systems with Nuvoton TPM 2.0 on I2C)
 ----------------------------------------------------------
 
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index a2688ac..6869093 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -944,6 +944,9 @@ int tpm_pm_suspend(struct device *dev)
 	if (chip == NULL)
 		return -ENODEV;
 
+	if (chip->flags & TPM_CHIP_FLAG_ALWAYS_POWERED)
+		return 0;
+
 	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
 		tpm2_shutdown(chip, TPM2_SU_STATE);
 		return 0;
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 1ae9768..0ce379c 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -146,6 +146,7 @@ enum tpm_chip_flags {
 	TPM_CHIP_FLAG_IRQ		= BIT(2),
 	TPM_CHIP_FLAG_VIRTUAL		= BIT(3),
 	TPM_CHIP_FLAG_HAVE_TIMEOUTS	= BIT(4),
+	TPM_CHIP_FLAG_ALWAYS_POWERED	= BIT(5),
 };
 
 struct tpm_chip_seqops {
diff --git a/drivers/char/tpm/tpm_of.c b/drivers/char/tpm/tpm_of.c
index 7dee42d7..e89276c 100644
--- a/drivers/char/tpm/tpm_of.c
+++ b/drivers/char/tpm/tpm_of.c
@@ -34,6 +34,9 @@ int tpm_read_log_of(struct tpm_chip *chip)
 	else
 		return -ENODEV;
 
+	if (of_property_read_bool(np, "powered-while-suspended"))
+		chip->flags |= TPM_CHIP_FLAG_ALWAYS_POWERED;
+
 	sizep = of_get_property(np, "linux,sml-size", NULL);
 	basep = of_get_property(np, "linux,sml-base", NULL);
 	if (sizep == NULL && basep == NULL)
-- 
2.9.3